Given that being a little bit more descriptive and detailed (Which exact Switch? which software version was it running before the failed update? what exact update procedure did you followed? did you verified dowloaded bin file hash? and so on...) is always a good thing when exposing an issue to others...have you tried to connect directly to Console port using the proper HP provided cable (as per HPE 5120 EI switch documentation)?
It should be a valid approach to start recovering.